1. Field of the Invention
The present application relates to a system for arresting aircraft that have overrun a runway end and methods for constructing such a system.
2. Description of the Related Art
Airport runways are configured to accommodate the takeoff and landing of multiple types of aircraft. While the overwhelming number of those events occur without incident, there may be times when an aircraft overruns its runway and needs to be arrested. One such method for arresting aircraft is to position an engineered material arresting system (EMAS) in the safety area past the end of the runway. The EMAS includes an energy dissipating, deformable, crushable, and/or compactible material that engages the aircraft wheels and slows the aircraft by dissipating its kinetic energy. The material in the EMAS is designed to compact and give way to the aircraft tires during an overrun event.
EMAS installations may be located at one or both ends of a runway. The EMAS may be subjected to jet blast loads from aircraft taking off away from the EMAS or taxiing past the EMAS. Those loads typically generate upward lift on the EMAS, which may result in damage to an uncovered bed of material. As a result, the integrity of the EMAS may be at least partially compromised, debris may be spread across the runway area, and the effectiveness of the EMAS may be reduced.
One method for countering the uplift forces has been to embed continuous geogrid walls within the bed of compactible material, the walls placed in the overrun direction of the bed. The geogrid is a mesh-like structure that attaches to the underlying pavement using one or more anchors along its length. The geogrid may protrude above the compactible material when that material is first placed, which makes grading the material more difficult, and slows down the installation process. Moreover, in the event of damage to the geogrid, repair efforts may require excavating large portions of the compactible material in order to replace a length of geogrid.
During overrun events, in which an aircraft leaves the runway and is arrested by the EMAS system, it has been observed that arresting loads on the aircraft can increase at higher aircraft exit speeds. Thus, some aircraft for some EMAS systems may have maximum exit speeds that are limited by landing gear loading rather than available EMAS length.
It has been observed that smaller, lightweight aircraft may lack the weight and tire loading necessary for effective engagement with the EMAS during an overrun event. In those situations, rather than the aircraft tires engaging and/or embedding with the EMAS material, they may roll over the EMAS with little or marginal vertical penetration into the material, which can result in reduced effectiveness of that system.